FIG. 1 depicts an anteromedial aspect of knee. The knee joint joins the thigh with the lower leg and consists of two articulations: one between the femur 1 and tibia 2, and one between the femur 1 and patella 3. It is the largest joint in the human body and is very complicated. The knee is a pivotal hinge joint, which permits flexion and extension as well as a slight medial and lateral rotation. Since in humans the knee supports nearly the whole weight of the body, it is vulnerable to acute injury.
The quadriceps tendon 4 connects the femur 1 to the patella 3 and the patellar tendon 5 connects the patella 3 to the tibia 2. The articular cartilage 6 ensures supple knee movement while the meniscus 7 serves to protect the ends of the bones from rubbing on each other and to effectively deepen the tibial sockets into which the femur 1 attaches.
The ligaments surrounding the knee joint offer stability by limiting movements and, together with several menisci and bursae, protect the articular capsule. Knee laxity, due to ligament injury, can cause significant instability to the knee joint thereby predisposing the joint to further instability and additional injury. The medial collateral ligament (MCL) 11 and lateral collateral ligament (LCL) 10 provide side to side stability of the knee joint. Injury to the MCL 11 or LCL 10 can result in lateral instability of the knee.
The anterior cruciate ligament (ACL) 8 is responsible for controlling the forward glide of the tibia 2 in relation to the femur 1. This movement is called “anterior tibial translation.” The ACL 8, in combination with the other ligaments, of a healthy knee joint restrict the rotation or twisting of the knee. Injury to the ACL 8 can result in rotational and anterior instability of the knee.
The posterior cruciate ligament (PCL) 9 is the primary restraint to post translation of the tibia 2 on the femur 1 and acts as a secondary restraint to varus/valgus movements and external rotation. Injury to the PCL 9 can result in posterior instability of the knee whereby the patient feels that the knee can “pop-out” of place. PCL 9 injuries are the least common form of knee instability injury.
An injury or tear of any one of the aforementioned ligament predisposes the knee joint to secondary injuries to the other ligaments, as well as to the meniscus 7 and articular cartilage 6 of the knee. Approximately 50% of all ACL 8 injuries occur in combination with damage to the meniscus 7, articular cartilage 6 or other ligaments (9, 10, 11). Protecting and supporting a weakened knee joint after injury or pre or post-operatively, from the medial, lateral or rotational forces exerted upon the knee during walking, squatting and other movements is the primary purpose of a knee orthosis device for knee instability. Unfortunately such knee orthoses do not always work, especially with in big or obese patients.
Supracondylar and Intracondylar Fractures of the Femur
The rounded ends of the femur are called condyles. There is a type of fracture of the lower end of the femur that starts above the condyles and may pass down into the joint. There is a great deal of variation in the pattern of these fractures. At one extreme is a simple transverse fracture which does not enter the joint. At the other there may be splintering of the bone and multiple fragments including joint surface. The more severe injuries are caused by high energy trauma and may be open fractures. Fractures of the kneecap and tibial plateau may be involved as well. These injuries are amongst the most challenging fractures to treat. FIGS. 1b and 1c show the conventional means to fix the fractures 19 in the supracondylar and intracondylar regions. Bone screws 21 with or without bone plates 20 are typically used to fix these fractures 19. Unfortunately, with fixation by these conventional techniques, there is generally no ability to bear weight on the leg and the leg may be unable to bend at the knee, causing reduced range of motion in the patient's leg after healing.
Tibial Plateau and Proximal Tibia Fractures
The flat parts of the tibia which form a joint with the femur are called the tibial plateau. On the outside, or lateral side, of the knee is the lateral tibial plateau and on the inside, or medial side, is medial tibial plateau. Compression forces may be too great for this region and the lower end of the femur may be driven into the tibial plateau on the inner or outer side—or occasionally both.
These are severe and troublesome injuries which damage the weight bearing surfaces of this major joint. The focus of treatment of a tibial plateau fracture is to restore the smoothness of the joint surface as best as possible. Like supracondylar and intracondylar fractures of the femur there is a wide spectrum of tibial plateau fractures ranging from simple injuries which damage one plateau to extensive fractures with many fragments and involvement of the shaft of the tibia. FIGS. 1d and 1e show the conventional means to fix the fractures 19 in the tibial plateau and proximal tibia regions. Bone screws 21 with or without bone plates 20 are typically used to fix these fractures 19. Again, with fixation by these conventional techniques, there is generally no ability to bear weight on the leg and the leg may be unable to bend at the knee, causing reduced range of motion in the patient's leg after healing.
Thus, there is a need in the art for an apparatus and method for stabilizing the knee in patients after ligament surgery and after fixation of supracondylar and intracondylar fractures of the femur or tibial plateau and proximal tibia fractures.